Demonstrating Warehousing Concepts Through Interactive Animations

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In this paper, we report development of interactive computer animations to demonstrate warehousing concepts, providing a virtual environment for learning. Almost every company, regardless of its industry, holds inventory of goods in its warehouse(s) to respond to customer demand promptly, to coordinate supply and demand, to realize economies of scale in manufacturing or processing, to add value to its products and to reduce response time. Design, analysis, and improvement of warehouse operations can yield significant savings for a company. Warehousing science can be considered as an important field within the industrial engineering discipline. However, there is very little educational material (including web based media), and only a handful of books available in this field. We believe that the animations that we developed will significantly contribute to the understanding of warehousing concepts, and enable tomorrow’s practitioners to grasp the fundamentals of managing warehouses.

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  • 1. Gurarslan, O., Guler, Y. H., Sahin, H., Ertek, G., Ozguven, K., Cacina, S. and Akkas, A. C. (2006)."Demonstrating warehousing concepts through interactive animations.” 5th InternationalSymposium on Intelligent Manufacturing Systems, Sakarya, Turkey.Note: This is the final draft version of this paper. Please cite this paper (or this final draft) asabove. You can download this final draft from Demonstrating Warehousing Concepts Through Interactive Animations Omer Gurarslan1, Yigit Huseyin Guler2, Hasan Sahin2, Gurdal Ertek2, Kutluk Ozguven2, Sehmuz Cacina 2, Ali Can Akkas2 1 Faculty of Management Sabanci University, Orhanli, Tuzla, 34956, Istanbul, Turkey 2 Faculty of Engineering and Natural Sciences Sabanci University, Orhanli, Tuzla, 34956, Istanbul, Turkey 1 / 17
  • 2. AbstractIn this paper, we report development of interactive computer animations todemonstrate warehousing concepts, providing a virtual environment for learning.Almost every company, regardless of its industry, holds inventory of goods in itswarehouse(s) to respond to customer demand promptly, to coordinate supply anddemand, to realize economies of scale in manufacturing or processing, to addvalue to its products and to reduce response time. Design, analysis, andimprovement of warehouse operations can yield significant savings for a company.Warehousing science can be considered as an important field within the industrialengineering discipline. However, there is very little educational material(including web based media), and only a handful of books available in this field.We believe that the animations that we developed will significantly contribute tothe understanding of warehousing concepts, and enable tomorrow’s practitionersto grasp the fundamentals of managing warehouses.Submission areas: Virtual Worlds, Manufacturing Systems EngineeringIntroductionWarehousingWarehousing is a critical function that can be found in almost every supply chain. Sincewarehousing typically is one of the top three cost contributors (together with transportation andinventory carrying costs), effective warehouse planning and management can significantlyincrease the competitiveness of a company. 2 / 17
  • 3. Typical operations in a warehouse are receiving of inbound materials, put away to reserve andforward storage/picking areas, replenishment of the forward areas from the reserve areas, andpicking, sorting, packing, and shipping orders. Warehouse planning and management beginswith determining the strategic decision of which distribution strategy to employ. Then, thetactical decisions of selecting the equipment and setting the warehouse layout are made.Another tactical decision is the allocation of product groups to the areas within the warehouse.The strategy of zoning divides the warehouse into weakly linked zones where order picking takesplace with dedicated labor for each zone. Another, important decision is whether to batch in thepicking of incoming orders or not. Finally, operational decisions such as determining the laborschedule and the routings of order pickers are made.The most comprehensive resources on warehousing that we have found and used in our workare the following:  Frazelle (2002) not only provides a fascinating introduction to warehousing concepts, but also gives great insight on how to operate a warehouse efficiently. This book is intended mainly for practitioners and does not include any mathematical models.  Bartholdi and Hackman (forthcoming) have made their lecture notes available on the Internet in the form of a book titled “Warehousing and Distribution Science”. This book, discusses the results of fundamental research studies on warehousing, besides serving as an introductory resource.  The Progress Group1, a logistics and supply chain consulting company, has made several white papers available at their web site. These papers are great reads for those interested in learning experts’ insights on a variety of topics in supply chain and warehouse planning.Our work is primarily based upon the information and insights presented in the above threeresources. We have singled out the concepts that we believe are crucial, and built interactiveanimations for each, as will be explained in detail in the next section.1 3 / 17
  • 4. E-LearningIn the last ten years, as in all disciplines, there have been attempts in the area of logisticsmanagement to train or educate students or workforce with the help of electronic learning anddistance education at various levels, including corporate training programs, blue collaremployee capabilities enhancement, masters programs and undergraduate level courses.Although there are many alternative definitions, a description can be “E-Learning is the use ofdigital and internet technologies to create experiences that educate our fellow human beings”(Horton 2001).It is possible to classify electronic learning activities from various aspects: Automation asopposed to the human tutor involvement, community management tools employed and the levelof interaction, amount of games and simulations as opposed to traditional reading materials. Inthe age of internet and computer animation based games as the primary pastime of students,and when there are a number of various possibilities that attract them including films oractivities, traditional classroom education that is not supplemented by some of the e-learningactivities such as interactive multimedia animations a valuable resource is not utilized.Therefore in this study it is decided that in the teaching of logistics planning interactiveanimations that are characteristic in online education are to be used. This approach is expectedto explain in depth the main concepts in warehousing.Macromedia FlashWe have used the Macromedia Flash software2 in creating our animations. The greatestadvantages of this software -that played role in our selection- are the following:  The animations created in Macromedia Flash can be viewed in practically any operating system and over the internet.  A great percentage of internet users already have Flash Viewer installed on their computers.2 4 / 17
  • 5.  The animation files have very small sizes, due to the use of vectoral graphics.  The Macromedia Corporation is owned by the Adobe Corporation3 which has a strong presence on the Internet and a great influence in the software industry. The well-known Adobe Acrobat format (.pdf files) is the universal format in the academic and business world.  The “action script” programming language within Macromedia Flash enables developers to create easy-to-use GUIs (Graphical User Interfaces) and offers many of the capabilities of a general purpose programming language (such as C++).In designing and implementing our animation one issue that we paid attention to was to makesure that all the animations share the same characteristics with respect to interface: We used thesame set of buttons, same set of font sizes and the same height-to-weight ratios in all theanimations. We believe that this approach will help the users to perceive the animations ascomponents of an integrated whole.Related WorkEngineering Education LiteratureOne can find articles in engineering education literature that present impressive educationalmaterials in various fields of engineering: Leung et al. (2001) report the development andclassroom use of an animated simulation package to teach electromagnetic theory. Ong andMannan (2002) describe a web-based courseware to teach concepts and principles inmetalworking, focusing on metallurgy aspects. Their system is developed using MacromediaFlash (as in our work) together with MS Front Page web authoring system. The last example thatwe have chosen to mention is the system developed by Ettouney et al. (2000) for the design and3 5 / 17
  • 6. simulation of thermal desalination process. This system has been used extensively in graduate,undergraduate, and training classes with great success.Internet ResourcesBartholdi has made available on the internet several computational tools4 to accompanyBartholdi and Hackman (forthcoming). One of these is a visualization program developed usingVisual Basic that reads a MS Access database and a MS Excel spreadsheet, and gives a coloredbird’s eye view of a warehouse. This tool can be used in warehousing education within anengineering curriculum.Another source available on the internet is the Interactive Warehouse5 Java applet created byRoodbergen. The Interactive Warehouse allows users to learn about methods for determiningorder picking routes, which were compared earlier in an article by Roodbergen and De Koster(2001). The applet walks the user through the steps of setting a warehouse layout, creating anorder, creating a route, selecting a routing method, and viewing the results.These are the only two sources that we have been able to find on the internet.The Animations DevelopedDistribution StrategiesThis animation illustrates the three basic distribution strategies of traditional distribution (witha warehouse), direct shipment, and crossdocking (Simchi-Levi et al., 2003, p133-136). Webelieve that this animation should be the first animation to show in an introductory4 6 / 17
  • 7. warehousing presentation, since it gives an overview and a general understanding of awarehouse (and a crossdocking facility) within the general context of a supply chain. Intraditional distribution the warehouse serves as a storage point, where products incoming fromthe suppliers are putaway to various locations in the warehouse to be stored for some time(which can be in the magnitude of years) and then picked for shipment to demand points(Figure 1a). Direct shipment takes place when the supplier sends its shipments directly todemand points, bypassing the warehouse (Figure 1b). In crossdocking, the suppliers’ trucks dovisit the so called “crossdock facility”, but the products are not stored for more than 24 hours(Figure 1c). Crossdocking can bring significant cost savings but should be carefully planned andcoordinated.Order Picking SchemesNext animation that we present summarizes the picking schemes in a warehouse. Freeformpicking takes place when there is no zoning in the warehouse. In this scenario, two possibilitiesare single order picking and the batch picking (Figure 2a). In single order picking, the orderpicker travels on a new route to pick each new order (Figure 1b). In batch picking, the orderpicker picks two or more orders on the same route.In zone picking, each order picker is allocated to a particular zone, and is responsible of pickingthe orders in his/her zone. Since the items within the same order may be picked at differentzones simultaneously, there is a need to combine these picks into a single whole. Two strategiesto achieve this are progressive assembly and downstream sortation. In progressive assembly thefirst order picker picks the items in an order that reside in his/her zone, and puts the tote/boxcontaining the incomplete order to the origin point for the second zone (Figure 2c). The nextorder picker seizes what the preceding order picker has accumulated and continues picking theitems in the order that reside in his/her region.In downstream sortation strategy, the order picker in each zone leaves the incomplete order thathe picked into a conveyor, and the conveyor carries the totes/boxes to a sortation point (Figure2d). 7 / 17
  • 8. (a) (b) (c) Figure 1. Distribution Strategies 8 / 17
  • 9. (a) (b)Figure 2. Picking Schemes in a Warehouse 9 / 17
  • 10. (c) (d)Figure 2 (continued). Picking Schemes in a Warehouse 10 / 17
  • 11. Pick-to-light SystemOrder picking in most warehouses involves minimal technology. A typical order picking tourstarts with receipt of a picking list, which displays the item number (also referred to as SKUnumber, standing for Stock Keeping Unit), the item location and the number of units to pick.The order picker sorts the items to be picked in his mind, and visits each item’s location to makethe picks (Figure 3a). Tasks that consume time during this classical mode of order picking aretraveling, searching, extracting and documenting. (a) 11 / 17
  • 12. (b) Figure 3. Pick-to-light SystemOne problem encountered in most order picking operations is the erroneous picking of items. Apick-to-light system is a solution that technology offers to reduce the times for the mentionedtasks and to reduce order picking errors (Figure 3b). In a pick-to-light system, an indicator lightand an electronic numeric display inform the order picker on where to pick from and in whatquantity. The order picker is relieved from the burden of searching the item locations and -to adegree- relieved from other tasks. Picking errors are also observed to decrease when pick-to-light systems are implemented. Thus the pick-to-light system is a viable option that can reducecosts and increase order picking accuracy in a warehouse.Bucket BrigadeLet us consider a forward pick area, where a number of order pickers (for example three ofthem) perform picking at varying speeds. A fundamental question is the following: How should 12 / 17
  • 13. the order pickers be placed on this picking line? Two alternatives that come to mindimmediately are sorting the pickers from the slowest to fastest and sorting them from the fastestto the slowest. Theoretical and empirical research by Bartholdi and Eisenstein (2006) show thatthe former is indeed the optimal alternative. The bucket brigade animation that we havedeveloped illustrates how this takes place through animation. The user can observe in the fast-normal-slow picker sequence (the simulation below) how the slow picker blocks the progress ofthe fast picker. In the slow-normal-fast picker sequence (operating mode) the fast picker clearsout any material downstream and takes over the work upstream from the slow picker. Figure 4. Bucket BrigadeCarouselCarousels are automated equipments that store small items in the shelves of their carriers andbring the items to order pickers (Figure 5). In practice two or three carousels are assigned to asingle order picker. This way the order picker can pick from other carousel(s) instead of waitingwhile one of the carousels is rotating. In our animation the order picker is given a pick list, and 13 / 17
  • 14. is responsible of picking from three carousels. The picker is able to initiate the rotation of eachof the carousels, and picks the items that are brought in front of him. When he is finished withpicking all the items in his list, he leaves his tote to a conveyor that will take it to the sortingarea. Figure 5. CarouselOrder Picker TruckAn order picker truck enables the order picker to pick items from high level storage locations(Figure 6). The normal operational mode in which the order picker truck uses in visiting picklocations is the “nearest neighbor” mode, where the picker visits the next closest pick location ateach step. An alternative mode of operation is the “sweep” mode, where the order picker picksall the items at a certain level before starting to pick the items in the next higher level. Ouranimation simulates and time wise compares these two modes of operation. 14 / 17
  • 15. Figure 6. Order Picker Truck Figure 7. Mobile Storage SystemMobile Storage SystemA mobile storage system is used to store items that are requested very infrequently (Figure 7).The main advantage of a mobile storage system is its space efficiency: There is only a single aisleempty at any time. When the picker is to pick an item from the system, the system creates anaisle dynamically to be able to make the pick. This system is typically used by media companies,state institutions and hospitals to store archived documents.ConclusionsWe have presented our work towards creating and integrating web-compatible educationalmedia into warehousing education. Our work is unique since we have not found any othersimilar work in the field of warehousing, except two web sites. 15 / 17
  • 16. Possible future work in this topic involves development of other media for warehousingeducation, including not only web based demonstrations/animations such as Java applets andFlash animations, but also interactive 3D models of warehousing equipment, as in the work ofOu et al. (2002). There is ongoing work going on at Sabanci University for developing sucheducational materials.One study that would contribute to the use of current media and further development ofeducational materials in the future is measuring the usefulness of the developed media. This canbe done through formal surveys with users (senior and junior students at Sabanci University)and analyzing the surveys thoroughly.ReferencesBartholdi, J. J. and Eisenstein, D. (2006) Bucket Brigades; available under, J. J. and Hackman, S. T. (forthcoming) Warehousing and Distribution Science; available electronically under, H., El-Dessouky, H., Al-Fulaij, H. and Al-Ansary, A. (2000) Computer Package for Design/Rating of Thermal Desalination Processes. Computer Applications in Engineering Education, vol: 8, 80-103.Frazelle, E. H. (2002) World-Class Warehusing and Material Handling. McGraw-Hill.Horton, W. (2001) Leading E-Learning. American Society for Training and Development.Leung W., Chen, Y. and Lee, Y. (2001) EM Wave Simulation: An Animated Electromagnetic Wave Teaching Package. Computer Applications in Engineering Education, vol: 9, 208-219.Ong, S. K. and Mannan, M. A. (2002) Development of an Interactive Multimedia Teaching Package for a Course on Metalworking. Computer Applications in Engineering Education, vol: 10, 215-228.Ou, S., Sung, W., Hsiao, S. and Fan, K. (2002) Interactive Web-Based Training Tool for CAD in a Virtual Environment. Computer Applications in Engineering Education, vol: 10, 182-193. 16 / 17
  • 17. Roodbergen, K. J. and De Koster, R. (2001) Routing methods for warehouses with multiple cross aisles. International Journal of Production Research, vol: 39, no: 9, 1865-1883.Simchi-Levi, D., Kaminsky, P. and Simchi-Levi, E. (2003) Designing and Managing the Supply Chain: Concepts, Strategies, and Case Studies. McGraw-Hill/Irwin. 17 / 17